Farmers in America have continually battled water shortage issues. The Ogallala aquifer is a rapidly-dwindling source of water that is being consumed faster than it can be replenished. Cycles in rainfall and weather are unpredictable, and farmers often resort to rationing water among their crops and livestock. Of course, putting less water on crops limits their ability to grow and produce, and in turn limits the profit for the farmer. However, many farmers find themselves in such predicaments because they simply do not have enough water to spread effectively.
Irrigation techniques have been developed to improve the efficiency with which water is stored, distributed, and used. Many farmers use center-pivot irrigation to irrigate their fields. Center-pivot irrigation systems typically have a main water pipeline extending from a central pivot to a distal end across several structural spans supported on moveable towers. Most center-pivot irrigation systems are one-quarter mile systems, such that they have lengths of about 1300 feet and irrigate a field of approximately 122 acres. A plurality of nozzles depend from the water pipeline along each span, often by hoses, drop pipes, or “goosenecks,” so that the nozzles are positioned just above the field of crops. The nozzles are typically spaced between thirty and ninety-six inches apart. The most common spacing between nozzles is sixty inches, such that a standard 1300-foot system includes approximately 260 nozzles.
When water is pumped and applied through the water pipeline and the towers drive around the central pivot, the field is watered in a circular fashion, producing a circular field. Center-pivot irrigation systems are very effective systems for applying water across a circular field, especially when the soil is consistent across the field, the sun exposure is consistent, the terrain is flat, and the same crop is planted across the field. In such situations, a farmer can easily determine the amount of water that must be supplied to the center-pivot irrigation system and also the rate at which the center-pivot irrigation system must rotate to provide the crops in the field with the necessary water.
Generally, however, in a field that is half a mile on one side, it is unlikely that a farmer's field is consistent in elevation, soil quality, sun, and crop type. Portions of the field may have fertile soil, and other portions may have poor soil. Some areas of the field may be higher, and others may be lower, to the extent that rain gathers in the low areas and forms water holes or ponds, or such that watering low areas would lead to standing water. Transitions between high and low elevations can change the duration and angle of sun exposure on a portion of the field. Farmers may plant different crops in sectors, which have pie-wedge shapes, or in arcs, perhaps because of the quantity of seed and desired yield, or perhaps because the soil in that portion of the field is more suitable for one type of crop over another. For these reasons and others, different parts of a circular field typically require different amounts of water. Further, different parts of a circular field often should be watered at different intervals. The farmer must thus plan carefully how crops are planted so as to be able to best water them; he may decide to plant crops in sectors and manually interrupt every rotation of the irrigation system to turn the water supply on or off depending on the needs of the sector, or he may actually choose to over-water some portions of the field or under-water other portions of a field. For example, a farmer can run a center-pivot irrigation system at the rate required by a crop in a first section of the field, putting a corresponding amount of water on the field. However, that rate of rotation and amount of water may be too great for a second section of the field, so that by watering to the demands of the first section, the farmer may be sacrificing the full potential of the crop in the second section. Not only does such a practice reduce the yield of the crop in the second section of the field, but it also distributes water unnecessarily and consumes more electricity than would be required with watering the entire field with one revolution of the irrigation system.
While some modern center-pivot irrigation systems apply only water, others apply a combination of water and chemicals, such as fertilizers or pesticides. In some systems, the chemicals are fed into the water pipeline at the center pivot from a tank containing the chemicals. The chemicals are then carried with the flow of water through the water pipeline to each span and expelled out the nozzles onto the field. Because the chemicals are introduced at the central pivot, the chemicals and water are mixed together and carried through the water pipeline, and the dispersal of chemicals across the field is regulated as described above, by regulating the pressure of the water and the speed of rotation of the center pivot irrigation system about the central pivot. Carrying chemicals in the same line as the water risks contamination of the water line, and the chemicals often corrode the water line over time, which can cause leakage of chemical and damage to the sprinkler requiring maintenance. An improved method for efficiently and effectively applying water and chemicals to a field is needed.